How to get String in a non activity class?

Question

I am new to android app developement.I did found questions related to my issue but none provide the correct solution. Here is my code where i am trying get string. I am getting error like this

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getString(int)' on a null object reference

public class CommonUtils {
    private static Context _context;

    public CommonUtils(Context context) {
        this._context = context;
    }
    public static String convertTimeToHoursMinutesString(long lTimeinMillis){
        // Calculate hours first.
        long hours = TimeUnit.MILLISECONDS.toHours(lTimeinMillis);
        lTimeinMillis -= TimeUnit.HOURS.toMillis(hours);
        // Calculate minutes then.
        long minutes = TimeUnit.MILLISECONDS.toMinutes(lTimeinMillis);
        lTimeinMillis -= TimeUnit.MINUTES.toMillis(minutes);
        // Calculate seconds last.
        //long seconds = TimeUnit.MILLISECONDS.toSeconds(lTimeinMillis);

        StringBuilder str = new StringBuilder(64);
        str.append(hours);

        str.append(_context.getString(R.string.Hour));
        str.append(minutes);
        str.append(_context.getString(R.string.Min));
        //str.append(seconds);
        //str.append(" Seconds");
        return(str.toString());
        }
    }

Does this answer your question? [getString Outside of a Context or Activity](https://stackoverflow.com/questions/4253328/getstring-outside-of-a-context-or-activity) — leopal, Nov 25 '19 at 10:44
Where is the code where you are calling `getString()` ? At which line you are getting this exception? — gprathour, Nov 25 '19 at 10:45
No..it only supports sytem resources..i have string.xml and i need to get that string in my class. @leopal — Jasmine Antony, Nov 25 '19 at 10:51

score 1 · Accepted Answer · answered Nov 25 '19 at 11:02

The issue which you are getting is NullPointerException on _context.

I think it is because you have declared _context as static variable and convertTimeToHoursMinutesString as static method.

But you are initializing the _context in constructor.

public CommonUtils(Context context) {
    this._context = context;
}

But as the method is static so you would not be creating an object to call it. Instead you would be calling it directly by class name, like CommonUtils.convertTimeToHoursMinutesString. So the constructor never gets called, hence _context is null.

If you want to keep it static then you can do it like this,

public static String convertTimeToHoursMinutesString(Context _context, long lTimeinMillis){
    // Calculate hours first.
    long hours = TimeUnit.MILLISECONDS.toHours(lTimeinMillis);
    lTimeinMillis -= TimeUnit.HOURS.toMillis(hours);
    // Calculate minutes then.
    long minutes = TimeUnit.MILLISECONDS.toMinutes(lTimeinMillis);
    lTimeinMillis -= TimeUnit.MINUTES.toMillis(minutes);
    // Calculate seconds last.
    //long seconds = TimeUnit.MILLISECONDS.toSeconds(lTimeinMillis);

    StringBuilder str = new StringBuilder(64);
    str.append(hours);

    str.append(_context.getString(R.string.Hour));
    str.append(minutes);
    str.append(_context.getString(R.string.Min));
    //str.append(seconds);
    //str.append(" Seconds");
    return(str.toString());
}

Also you can access getString() like context.getResources().getString(R.string.YOUR_STRING);

Is there any way to initialize string array by using (R.string.thatvalue) ??? — Jasmine Antony, Nov 25 '19 at 12:02
@JasmineAntony Check this, it might help you. https://stackoverflow.com/q/4161256/1055241 — gprathour, Nov 25 '19 at 12:08
I want to initialize in my enum class eg..public enum WorkStateEnums { WORK_EMPTY_CAR(000, "WORK_EMPTY_CAR", R.string.xyz);} — Jasmine Antony, Nov 25 '19 at 12:22
@JasmineAntony Try it out first, if you face any issues first try to understand it and fix it yourself, if it doesn't work then you can post a new question here. — gprathour, Nov 25 '19 at 12:28
Hi i am getting NullPointerException (Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference) — Jasmine Antony, Dec 05 '19 at 06:21
@JasmineAntony Hello, I think that we solved that day, when you posed this question. — gprathour, Dec 05 '19 at 07:52

score 0 · Answer 2 · answered Nov 25 '19 at 10:59

0

in your code

str.append(_context.getString(R.string.Min));

please replace it with

str.append(_context.getResources().getString(R.string.Min));

answered Nov 25 '19 at 10:59

unownsp

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How to get String in a non activity class?

2 Answers2